Carbon Capture: Retrofit or start from scratch?

Carbon Capture and Storage (CCS) is much in the news. Fluor, for example, has 30 years of experience with its own carbon capture technology across 400 carbon capture units. As an EPC contractor. Fluor spoke about this topic at the recent PowerGen International conference in Dallas.

Marcus Weber, the company’s Executive Process Director, posed the question: “When implementing natural gas combined-cycle (NGCC) plants with CCS, should you retrofit existing facilities or build from scratch?” Two factors support doing both::

Unprecedented demand for power: North American Electric Reliability Corp (NERC) forecasts 78 GW of winter peak demand growth over the next 10 years, double its forecast from two years ago, with natural gas providing the bulk of this energy. “We are experiencing the largest growth in power demand since the years following World War II,” said Ed Baine, President of Dominion Energy Virginia.
EPA regulations require that new gas facilities achieve such a low volume of greenhouse gas (GHG) emissions that can only be achieved by the application of CCS technology.

It depends on whether it is cheaper, eventually, to retrofit existing plants with CCS or to build everything from scratch. The retrofit option provides immediate benefits: lower capital investment, faster deployment, and the leveraging of existing assets.

Building anew provides owner operators the opportunity to optimize the design by integrating the power plant and carbon capture processes. Further, they can free themselves from the generally higher emissions profile of older technology and adopt the latest generation of gas turbines.

Sometimes a retrofit will work well over a 30-year lifespan. At other times, however, new builds make more sense – especially for aging facilities. “Amine-based solvents are the most proven and prevalent approach for post-combustion carbon capture,” said Weber. Solvent selection may prove the deciding factor.”

As gas is a lot cleaner than coal, its CO₂ concentration in the flue gas is typically at around 3-5% of volume. A high volume of gas needs to be treated per ton of CO₂, which raises CAPEX.

However, the flue gas has 13-15% O₂ concentration, which increases amine degradation rates. This can lead to diminishing performance if not replaced. Amine waste material also may be a disposal problem.

Fluor’s Ecomamine FG Plus (EFG+) technology for post-combustion, deployed in about 30 plants, is designed for low-pressure gas streams containing 3% to 20% CO₂ and 1% to 15% O₂. “Treating the solvent is key to performance as it degrades over time,” said John Gilmartin, Director of Carbon Capture Technology.

He cited the Bellingham combined cycle plant In Massachusetts using CCS to remove 330 metric tons per day of CO₂. It uses air cooling, although high ambient temperatures hurt efficiency during summer. It is the only commercial CO₂ recovery unit in the world operating on gas turbine flue gas with an on-stream factor of 98.5%.

Over the last couple of decades, the technology for CCS has steadily improved. Since 2000, Fluor has lowered CCS energy consumption by 36% reduced solvent losses by 70%, and cut volatile organic compound (VOC) emissions by 10 to 20 times and ammonia emissions by five times. The company is delivering another 13 commercial-scale EFG+ units, which will add up to over 20 million metric tons of CO₂ capture per year

“We have developed a solvent maintenance system to reclaim solvent rather than heating to boil off contaminants, which only causes more degradation,” said Gilmartin. “As a result, we lose 2-3% of our amine per ton of CO₂ capture whereas others lose 30%.”

One recent project is the Elk Hills Power Plant in California that runs two GE Vernova 7FA gas turbines and a D-11 steam turbine. It captures 4,000 million tons of CO₂ per day at a 90% removal rate.

As for the retrofit v new build debate, Weber laid out some key considerations:

Does the old plant have enough life left to justify carbon capture investment.
To keep costs down, it is best to locate CCS equipment close to the HRSG stack.
The CAPEX and OPEX trade-off must be carefully reviewed over the lifespan of the plant.
A retrofit will lower power output as some load must be added to run the carbon capture equipment.

“In many cases, a well-integrated new-build project will optimize processes. It will lower overall costs and provide a better heat rate as a result,” said Weber.